1. Field of the Invention:
The present invention is directed generally to the automatic protection of equipment and, more specifically, to the automatic protection of pumps.
2. Description of the Prior Art:
In present fluid systems 9 (FIG. 1) incorporating a centrifugal pump 10, it is possible for the tank or other suction source 11 to be emptied or drained to a level such that the potential for vortex formation or air entrainment exists. Additionally, the inadvertent closing of a suction line isolation valve 14 can cause the pump to experience a total or partial loss of suction fluid. Any of these events can cause pump damage due to rotating element heat up, fluid cavitation, or air-binding of the pump casing and rotating element.
Current practice directed to the mitigation of pump damage due to loss of suction suggests the use of one of two methods of indicating loss of fluid level. In one method, a sight glass or section of clear plastic hose 12 in the pump suction source is provided as a direct visual indication of the sufficiency of fluid level. The second method incorporates a fluid level sensor 13 which alerts the operator of a low fluid level situation. There are, however, inadequacies inherent in both of these two methods of fluid level indication. In either method, the operator must recognize the low fluid level indication and must then react with the appropriate precautionary or mitigating procedure. Operator recognition and reaction times are on the order of several minutes whereas required protection steps must often be taken within seconds of the initiating event. In addition, the first method requires the operator to be present in order to make the necessary visual inspection.
The instance may occur where an operator is not present when an abnormal condition occurs or it may take several minutes for the operator to recognize the problem and take appropriate corrective action. For pumps costing tens of thousands of dollars, pumps located in hazardous environments such as a nuclear containment building, or pumps located in inaccessible locations, the protection methods of the prior art are clearly inadequate. Accordingly, the need exists for a system which is capable of automatically detecting abnormal conditions in a fluid system and automatically initiating pump protective action.